Integration and Electrical Evaluation of Epitaxially Grown Si and SiGe Channels for Vertical NAND Memory Applications

Epitaxially grown Si and Si_0.6Ge_0.4 are integrated as replacement of poly-Si channel in vertical cylindrical transistors for vertical NAND memory application, in order to investigate the impact of the grain boundaries on current conduction. Epi-Si outperforms both poly-Si and Epi-SiGe channels, resulting in the best conduction, with large improvement on both sub threshold swing and transconductance (g_m). The experimentally observed g_m bimodal distribution for epi Si is corroborated and explained through a resistive network model: lower g_m conduction occurs when current needs to cross a high resistance boundary, whereas higher g_m is obtained when this boundary is not present.